This entry was written by Natasha Black as part of a project done in BIAN 2133 ‘Human Reproductive Strategies’ at The Australian National University in 2019 Semester 2.
Introduction:
Homogamy in humans is where males and females tend to marry someone that is similar to them and can be contributed to people choosing mates similar to themselves or due to positive sexual imprinting (Nojo, Tamura & Ihara, 2012). Sexual imprinting is a factor in mate choice where offspring use the physical characteristics in people they know, usually closely related to such as opposite sex parents, to either choose mates or avoid mates. Positive sexual imprinting is where offspring use their opposite sex parent as a model for their future partners and can be potentially influenced by the relationship between offspring and parent. While negative sexual imprinting, also referred to as the “Westermarck Effect”, is where offspring avoid choosing mates from people that they have grown up with during infancy and early childhood. Sexual imprinting, both positive and negative, have been found to be quite significant in some non-human animals but is variable in different human populations with having a notable effect to not having any effect on mate choice.
Main Text:
Positive Sexual Imprinting:
Positive sexual imprinting in humans in relation to mate choice is where offspring have preferences for facial features that are similar to their opposite-sex parent. An example of this was an experiment which observed if the eye colour of a woman’s father impacted the male she might choose as a mate. This was done by showing each male face to a woman twice, one with light eyes and the other with dark eyes and the preference was recorded. It was found that women that had a father with light coloured eyes were more likely to pick a mate which also had light coloured eyes. However, there was no significant preference seen in women for a male with dark coloured eyes if their father had dark coloured eyes (Bressen & Damian, 2018). Another example is an experiment where 70 heterosexual people were examined to see if they had chosen partners that were similar to their opposite sex parent. This was done by showing participants photos of the 70 heterosexual people and rated how similar the person’s partner was to their opposite sex parent. In this experiment, it was observed that there was no real similarity seen in a woman’s partner and her father but there was similarity between a man’s partner and his mother (Rantala & Marcinkowska, 2012). Both of these experiments help to demonstrate that positive sexual imprinting can have a variable impact on mate choice in humans but each experiment shows the opposite results of the other which highlights how weak positive sexual imprinting can be in mate selection.
The effect of positive sexual imprinting on mate choice is also affected by the relationship that is present between parent and offspring. When there is a positive relationship between an offspring with their opposite sex parent, it is more likely that positive sexual imprinting can take place. The formative years when this imprinting takes place is thought to be before children enter puberty, around 6 to 8 years of age (Nojo, Tamura & Ihara, 2012). An example of this was an experiment where the facial preferences of children that were about to enter puberty were recorded and the relationship with their parents was recorded as well. It was found that children that had a positive relationship with their opposite-sex parent was more likely to choose facial features that were similar to that parent (Vuckovic et al, 2015). This was supported in another experiment where women who had adoptive fathers had their mate choices examined to see if they picked a mate that had similar facial features to their adoptive father when there was a positive relationship. Participants were given pictures of women and four possible husbands, one being the actual husband, and were rated on how similar they were to the woman’s adoptive father. It was observed that women that had a positive relationship with their adoptive father had a spouse with more similar facial features to the adoptive father compared to women that didn’t have a positive relationship with their adoptive father (Bereczkei, Gyuris & Weisfeld, 2004).
Negative Sexual Imprinting:
Negative sexual imprinting is a mechanism used in mate choice to reduce the chance of incestuous activities that can have negative genetic consequences and occurs by making those a person grows up with less desirable as a sexual partner. This is supported in a number of studies with one being in Finland where they looked at the prevalence of incestuous relationships between biological fathers and their daughters and step-fathers and their step-daughters. It was observed that there was a higher prevalence of incestuous relationships between a step-father and step-daughter compared to incestuous relationships between a biological father and daughter. This higher prevalence suggests that there is a mechanism in place, such as negative sexual imprinting, that stops the formation of sexual attraction to those biologically related. A drawback to this particular study was that they didn’t specify if the step-father had been around as the daughter was growing up in their formative years when negative sexual imprinting would take place (Rantala & Marcinkowska, 2011). However, as there is still evidence of incestuous relationships, negative imprinting isn’t a strong force in mate selection.
Conclusion:
Sexual imprinting is a mechanism seen in mate choice that can affect the type of mate a person will choose and can either be positive or negative. Positive sexual imprinting in mate choice is where a person chooses a mate based off physical similarity to their opposite sex parent. This is supported by observing in both heterosexual men and women, there have been higher cases of their partner being similar to their opposite sex parent. However, positive sexual imprinting can be affected by the quality of the relationship between the opposite-sex parent and the offspring. This is seen in experiments where facial preferences are observed when the relationship with their opposite parent is known and it was more likely that there was similarity in the facial preference to the opposite sex parent when the relationship was positive. Negative sexual imprinting, also referred to as the Westermarck effect, is where offspring avoid choosing people that they have grown up closely with as mates. This can be seen in studies that have looked at the prevalence of incestuous relationships and observed that it was less common in those that were biologically related, assuming they have grown up closely together, compared to step parents.
References:
Bereczkei, T., Gyuris, P & Weisfeld, G. 2004. Sexual imprinting in mate choice. Proceedings of the Royal Society B, Biological Sciences, 271(1544), 1129-1134.
Bressan, P & Damian, V. 2018. Fathers’ eye colour sways daughters’ choice of both long- and short-term partners. Scientific Reports, 8, 1-9.
Nojo, S., Tamura, S & Ihara, Y. 2012. Human Homogamy in Facial Characteristics. Human Nature, 23(3), 323-340.
Rantala, M & Marcinkowska, U. 2011. The role of sexual imprinting and the Westermarck effect in mate choice in humans. Behavioural Ecology and Sociobiology, 65(5), 859-873.
Rantala, M & Marcinkowska, U. 2012. Sexual Imprinting on Facial Traits of Opposite-Sex Parents in Humans. Evolutionary Psychology, 10(3), 621-630.
Vukovic, J., Boothroyd, L., Meins, E & Burt, M. 2015. Concurrent parent-child relationship quality is associated with an imprinting-like effect in children’s facial preferences. Evolution and Human Behaviour, 36(4), 331-336.